Why Does My Toilet Keep Running? The 10 Minute Fix

Why does my toilet keep running?

A toilet runs for one of two reasons. Either water is leaking out of the tank and the fill valve keeps topping it back up, or the fill valve never shuts off and the extra water pours down the overflow tube. Everything else is detail. Work out which of those two is happening and you have cut the job in half.

Take the tank lid off and set it flat on a towel so it does not chip. Flush once, then watch. The tank should fill, the valve should click off, and the water should sit dead still after that. If the level creeps down over the next few minutes, water is escaping through the flapper at the bottom. If the level holds but a steady trickle runs into the open pipe standing up in the middle of the tank, the fill valve is your problem.

How much water does a running toilet waste?

More than it sounds like, because it leaves quietly. A fill valve stuck open moves three to five gallons a minute, which New York City's water department puts at up to 4,000 gallons a day going straight into the sewer. See the department's page on detecting toilet leaks. Its printed leak brochure sizes the slower ones: 30 gallons a day for a small leak, 250 for a medium one, and up to 6,000 a day at the bad end.

If what you actually want is to confirm the toilet is what moved your bill, and what your water district will do about it, that is covered in our walkthrough on a water bill that jumped. This one is about the parts.

How do I replace a toilet flapper?

Most running toilets need this repair and nothing more. The part is usually under $15 on a hardware store shelf.

1. Shut the angle stop, the small valve on the wall behind the toilet. Clockwise until it stops.
2. Flush, and hold the handle down to drain the tank.
3. Unhook the chain from the flush lever, then slide the flapper ears off the pegs on the overflow tube.
4. Take the old flapper to the store with you. Flappers are not universal. A 2 inch and a 3 inch are obvious side by side and impossible from memory.
5. Snap the new one on, hook the chain back up, open the angle stop, let the tank fill.
6. Flush twice and watch the level hold.

While the tank is empty, run a finger around the seat the flapper lands on. A nick or a rough ridge means the new flapper will leak too. Sediment and mineral scale cut those seats over the years, and once that happens the flush valve has to come out rather than the flapper.

The chain is the part people get wrong

Too tight, and the flapper never fully seats, so the toilet trickles all night. Too loose, and the chain loops under the flapper and props it open. Fluidmaster's instruction sheet gives the method plainly: hold the flush lever all the way up inside the tank, pull the chain tight so the flapper lifts as high as it goes, and clip it to the hole directly above the flapper. Then let go and watch the flapper drop flat. If it will not seat, let the chain out a link or two.

How high should the water in the tank be?

Half an inch below the top of the overflow tube. That is the number Fluidmaster prints on its own fill valve instructions, and it matters in both directions. Too low and the bowl does not get enough refill water to flush properly. Too high and water spills over the overflow tube around the clock, which looks and sounds exactly like a leak.

Two more measurements off the same sheet, for anyone swapping the whole fill valve. The top of the overflow tube has to sit at least an inch below the hole the flush lever passes through. And the C.L. mark stamped on the side of the fill valve has to end up an inch above the top of the overflow tube. That second one is a code requirement in Fluidmaster's printed instructions, not a suggestion. It is the air gap that stops tank water from being drawn back into the drinking water in your house.

Why did the flapper go bad in the first place?

• Drop-in tank tablets. The bleach ones chew up rubber. Fluidmaster's warning is blunt: in-tank cleaners containing bleach or chlorine damage tank components, may cause flooding, and void the warranty. A blue tablet sitting in your tank is usually the whole explanation.
• Grit on the seat. Sediment leaves small cuts in the flush valve, and no flapper seals against a cut. This is the common one in older houses around Sonoma and Marin, where the tank hardware has had 20 years of mineral scale running over it.
• Pressure swings. A fill valve can get pushed off its seat when house pressure spikes. If the toilet is not the only fixture acting up, start with house water pressure instead of buying toilet parts.

When should I stop and call a plumber?

Call when the tank still runs after a new flapper and a correctly set chain. Call when the flush valve seat is cut, when the tank bolts weep, when the porcelain shows a hairline crack, or when the toilet is old enough that nothing on the shelf fits it. A flapper and a fill valve are a short visit. Pulling the tank off the bowl to change a flush valve is the job where a Saturday repair turns into a wet bathroom floor.

CNTRline does toilet, faucet, and valve work across Sonoma and Marin County under faucet and fixture repair. Most quotes cost nothing, someone picks up the phone every day of the week, and you get a price before anybody starts. Call (707) 308-5599.